The present invention relates to a liquid filtration system and method for removing dissolved organic and inorganic contaminants and pollutants and particulate matter from a liquid.
Prior art filtration devices include activated carbon, ion-exchange resins, polymeric absorbents, submicron membranes and other filter media. Filtration devices containing activated carbon, ion-exchange resins, macro-reticulated styrene, and other polymeric absorbents are only capable of filtering at very slow filtration rates. In addition, oftentimes known filtration systems require considerable pre-filtration to prevent filter media blinding due to particulate, colloidal and protein coating of the filtration media. Submicronic filtration media and devices require considerable fluid pressure. The pores of the materials of construction of submicronic media are quickly blinded or clogged. In addition, when these prior art filtration devices are used in combination, the flow rates and differential pressures are set by the last in-line filter. If the last in-line filter is a filter utilizing standard submicronic membrane technology, flow rates can be as slow as milliliters per minute per square foot of membrane surface area. Prior art filtration devices have limited applications, short life spans and expensive replacement costs.
Some conventional state-of-the-art technology employing granular or spherical shaped filter media are subject to tunneling at high flow rates. In addition, conventional granular or spherical shaped filter media encapsulated in non-woven fibers by acrylic binders, have reduced absorption capacity because many of the pores are closed by the acrylic binder. Each of the above granular or spherical shaped filter media, if combined with state-of-the-art membrane technology result in very low flow rates and high differential pressures. These low flow rates and high differential pressures produce high sheer forces which cause elution of sorbate solutes and severely limit the function, in a short period of time, of these state-of-the-art chemical filtration media.
A major problem associated with conventional filtration systems confronting American industry, has been the high cost of replacing fouled ion-exchange resins and reverse osmosis (RO) membranes. Ion-exchange resins and RO membranes are subject to permanent fouling when they become coated with colloids and colloidal suspensions. High concentrations of metallic ions and organic carbons also foul ion-exchange resins and RO membranes.
Another problem associated with conventional filtration systems is the removal of dissolved organic contaminants in potable water. Dissolved organic contaminants are undesirable in potable water. These dissolved organics are generated by rainwater runoff, entropy and other environmental disturbances, and can be found in potable water from community and regional reservoirs. Dissolved organic contaminants also interfere with various manufacturing processes which require water containing low levels of dissolved organics. Traditional filtration technology including carbon filters, carbon-exchange resins, ion-exchange resins, micro-filters, diatomaceous earth filters and combinations of these filters have proven unsuccessful for removing dissolved organic contaminants from potable water and water used in manufacturing processes.
Recent advances in filtration technology including Zeta charged filters, Zeta charged diatomaceous earth filters and low molecular weight membrane ultra filtration (300 MW) reverse osmosis filters have also proved inadequate to the task of removing undesirable dissolved organics from potable water systems. Zeta charged filters require additional pre-filters which blind too quickly. In addition, the Zeta-filtered water was found to contain dissolved organic contamination. Zeta charged diatomaceous earth filters also proved to be inadequate due to slow filtration rates, rapidly blinded filter media, and the filtrate contained unacceptable levels of contaminants. Reverse osmosis (RO) systems (300 MW) also gave unacceptable results due to rapid fouling of the pre-filters and fouling, within 48 hours, of the RO membrane with organics. Further, the maximum water filtrate in a 24 hour period, under adverse conditions including high levels of metal ions, colloidal suspensions, suspended solids and dissolved organics, is generally less than 10,000 gallons at a prohibitive operating cost of about 2,400-3,000 dollars per day for membrane and filter media replacements.
Conventional carbon filters are generally unable to remove toxic contaminants at flow rates above 5 gal/min/square foot of carbon. Carbon filters also undergo rapid desorbing of the toxic contaminants from the carbon media back into the filtrate. Carbon filter media may also experience phosphate leaching in the range of 5-10 mg/l causing microalgae growth in water pipes and clogged particulate pre-filters in tap water supplies.
Conventional filtration technology is also unable to remove substances which have been added to potable water during municipal water processing. Many municipal water utilities add polyphosphates and water soluble polymers to their potable water systems. The polyphosphates and water soluble polymers prevent mineral plating on transport piping. Conventional filters have proven unacceptable for the removal of polyphosphates and water soluble polymers from potable water before consumption. Simple micron particle filtration results in blinding of the filter media in a short period of time. Particle filtration (micron), in combination with carbon filtration, also results in a low quality filtrate. The filtrate was loaded with phosphate, dissolved organics and particulate. In addition, Zeta charged diatomaceous earth filters are blinded rapidly so that phosphate and dissolved organics by-pass the media and remain in the filtrate. The membranes of reverse osmosis filters are rapidly clogged, and consequently permit by-pass of phosphates and metallic ions.
U.S. Pat. No. 4,076,619 to Howery discloses hydrophilic polymeric formulations which, when applied to various matrix materials, act as filters by means of molecular absorption chemical filtration in both marine and fresh water systems. Howery further discloses application of hydrophilic polymeric materials as a film-forming coating and as a pellet form of filtration media.
U.S. Pat. No. 4,620,932 to Howery discloses a one-piece construction continuous matrix submicronic filter media capable of high volume filtration of submicronic sized particulate from fluids. The submicronic filter media does not require the addition of wetting agents, solvents, added electrical charge enhancers or elevated pressure differentials to maintain flow rates of 20-150 gallons/minute (gal./min., GPM) at absolute particle micron ratings as low as 0.1.
While there have been attempts to develop filtration systems which employ high flow rates for the removal of organic and inorganic solutes and particulate from liquids, these approaches often lack the efficiency necessary for practical implementation. Typical problems encountered in using state-of-the-art filtration systems employing high flow rates are blinding and clogging of the filter media, by-passing of dissolved organic and inorganic solute contaminants and expensive filter media replacement costs. Consequently, there is a need for alternative high flow rate filtration systems for the removal of organic and inorganic solutes which address the problems typically associated with high flow rate filtration systems.
It is therefore an object of the present invention to provide a filtration system and method for the efficient, continuous and economic removal of dissolved pollutants and contaminant particulate at flow rates thousands of time greater than submicron membrane and other state-of-the-art filtration media and devices.
It is a further object of the present invention to provide a filtration system/method having the flexibility for application with liquids of varying viscosity, from that of heavy petroleum to that of water.